feat: adds get event by id route

[ricardogarim]

Summary by CodeRabbit

• New Features

  • Added a federation API endpoint to fetch an event by ID, returning origin_server_ts, origin, and PDUs.

• Improvements

  • Consistent server origin embedded in responses.
  • Clearer, typed error responses for the new endpoint (401/403/404/500).
  • Added descriptive route metadata for federation endpoints, including the transaction send route.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.42%. Comparing base (76956e6) to head (a47b32a).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #175   +/-   ##
=======================================
  Coverage   80.42%   80.42%           
=======================================
  Files          58       58           
  Lines        4516     4516           
=======================================
  Hits         3632     3632           
  Misses        884      884           

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[coderabbitai]

Caution

Review failed

The pull request is closed.

Walkthrough

Adds GET /_matrix/federation/v1/event/:eventId and related DTOs; integrates ConfigService into federation transactions controller; refactors route registration to chained app.put(...).get(...); GET returns event PDUs with embedded origin and origin_server_ts or a standardized error.

Changes

Cohort / File(s)	Summary
Federation Transactions Controller packages/homeserver/src/controllers/federation/transactions.controller.ts	Introduces ConfigService via container.resolve; refactors route registration to a fluent chain (app.put(...).get(...)); adds GET /_matrix/federation/v1/event/:eventId handler using GetEventParamsDto, returns GetEventResponseDto on success (embedding origin from ConfigService and origin_server_ts) and GetEventErrorResponseDto on error; retains PUT /_matrix/federation/v1/send/:txnId with metadata.
Federation DTOs for GetEvent packages/homeserver/src/dtos/federation/transactions.dto.ts	Adds GetEventParamsDto, GetEventResponseDto, GetEventErrorResponseDto and exported types GetEventParams / GetEventResponse; no other DTO changes.

Sequence Diagram(s)

sequenceDiagram
  autonumber
  participant C as Federation peer
  participant HS as Homeserver App
  participant TC as TransactionsController
  participant ES as EventService
  participant CS as ConfigService

  rect rgb(240,248,255)
    note over C,HS: GET /_matrix/federation/v1/event/:eventId
    C->>HS: HTTP GET /event/:eventId
    HS->>TC: invoke GET handler (params validated)
    TC->>ES: getEventById(eventId)
    ES-->>TC: event | null
    alt event found
      TC->>CS: read serverName
      CS-->>TC: origin (serverName)
      TC-->>C: 200 { origin_server_ts, origin, pdus:[ event(with origin) ] }
    else not found
      TC-->>C: 404 { errcode: M_NOT_FOUND, error }
    end
  end

Loading

sequenceDiagram
  autonumber
  participant FP as Federation peer
  participant HS as Homeserver App
  participant TC as TransactionsController

  rect rgb(245,255,245)
    note over FP,HS: PUT /_matrix/federation/v1/send/:txnId
    FP->>HS: HTTP PUT { pdus, edus }
    HS->>TC: invoke PUT handler
    TC-->>FP: 200 { pdus:[], edus:[] } or 400 on invalid
  end

Loading

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• feat: adds get event by id route #175 — Adds same GET /_matrix/federation/v1/event/:eventId route and GetEvent DTOs; appears to overlap on controller and DTO changes.

Suggested reviewers

• ggazzo

Poem

I hop through routes where events are found,
New paths bloom softly without a sound.
A timestamp twinkles, an origin bright,
PDUs tucked in, all snug for the night.
I nibble DTO carrots and do a small dance—🥕🐇

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title Check	✅ Passed	The title "feat: adds get event by id route" accurately and concisely summarizes the primary change in this PR — adding a GET event-by-id route (and associated DTOs) — and is clear for teammates scanning history.
Docstring Coverage	✅ Passed	No functions found in the changes. Docstring coverage check skipped.

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📜 Recent review details

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Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 66fdcf3 and a47b32a.

📒 Files selected for processing (2)

• packages/homeserver/src/controllers/federation/transactions.controller.ts (1 hunks)
• packages/homeserver/src/dtos/federation/transactions.dto.ts (1 hunks)

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[coderabbitai]

Actionable comments posted: 4

♻️ Duplicate comments (1)

packages/homeserver/src/controllers/federation/transactions.controller.ts (1)

17-41: Prior feedback addressed: routes are properly chained.

The .put().get() chaining resolves the earlier review note.

🧹 Nitpick comments (4)

packages/homeserver/src/dtos/federation/transactions.dto.ts (4)

32-34: Validate Matrix event ID format.

Early-validate :eventId to reduce unnecessary lookups and 404s.

 export const GetEventParamsDto = t.Object({
-	eventId: t.String({ description: 'Event ID' }),
+	eventId: t.String({
+		description: 'Event ID',
+		// Matrix event IDs look like `$something:server`
+		pattern: '^\\$.+:.+$',
+	}),
 });

---

36-42: Constrain response to exactly one PDU.

Contract says “single PDU”; enforce it in the schema.

 export const GetEventResponseDto = t.Object({
 	origin_server_ts: t.Number({ description: 'Origin server timestamp' }),
 	origin: t.String({ description: 'Origin server' }),
 	pdus: t.Array(EventBaseDto, {
-		description: 'An array containing a single PDU',
+		description: 'An array containing a single PDU',
+		minItems: 1,
+		maxItems: 1,
 	}),
 });

---

1-2: Optional: Reuse TimestampDto for consistency.

Align the top-level origin_server_ts with the scalar used in events.

-import { EventBaseDto } from '../common/event.dto';
+import { EventBaseDto, TimestampDto } from '../common/event.dto';

-	origin_server_ts: t.Number({ description: 'Origin server timestamp' }),
+	origin_server_ts: TimestampDto,

---

44-47: Unify error DTOs across federation endpoints.

Consider a shared FederationErrorResponseDto to avoid divergence with ErrorResponseDto and keep err shapes consistent.

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 4247c69 and 66fdcf3.

📒 Files selected for processing (2)

• packages/homeserver/src/controllers/federation/transactions.controller.ts (1 hunks)
• packages/homeserver/src/dtos/federation/transactions.dto.ts (1 hunks)

🧰 Additional context used

🧬 Code graph analysis (2)

packages/homeserver/src/dtos/federation/transactions.dto.ts (1)

packages/homeserver/src/dtos/common/event.dto.ts (1)

• EventBaseDto (19-36)

packages/homeserver/src/controllers/federation/transactions.controller.ts (3)

packages/federation-sdk/src/services/config.service.ts (1)

• ConfigService (74-147)

packages/homeserver/src/dtos/federation/transactions.dto.ts (5)

• SendTransactionBodyDto (8-21)
• SendTransactionResponseDto (23-30)
• GetEventParamsDto (32-34)
• GetEventResponseDto (36-42)
• GetEventErrorResponseDto (44-47)

packages/homeserver/src/dtos/common/error.dto.ts (1)

• ErrorResponseDto (3-6)

🔇 Additional comments (2)

packages/homeserver/src/dtos/federation/transactions.dto.ts (1)

52-53: Type exports look good.

packages/homeserver/src/controllers/federation/transactions.controller.ts (1)

62-67: Align declared 401/403/500 responses with behavior.

Either add auth/permission checks that set these statuses or remove them from the schema to avoid misleading OpenAPI.

Option A: keep and implement (preferred).
Option B (schema-only):

 				response: {
-					401: GetEventErrorResponseDto,
-					403: GetEventErrorResponseDto,
-					500: GetEventErrorResponseDto,
 				},